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Hydraulics/Transcript
Transcript Text reads: The Mysteries of Life with Tim & Moby A man, Tim, and a robot, Moby, are shown in a kitchen. Tim is playing with a toy excavator. MOBY: Beep! An animation shows Moby laughing at Tim. TIM: It’s not a toy! It’s a scale model. An animation shows Moby hand Tim a letter. Tim reads from the typed letter. TIM: Dear Tim & Moby, What exactly are hydraulics? It sounds cool but I don’t really get it. Thanks, Pip. TIM: Hydraulics is an area of engineering in which fluids are used to do work. It’s been around since the beginning of human history! Ancient civilizations in Mesopotamia and Egypt dug irrigation canals to water their crops. An image shows a narrow water way running through a desert. TIM: The Ancient Romans built huge aqueducts to transport water over long distances, and in medieval China, water wheels and dams harnessed the power of flowing water. The screen is divided into two equal sections. In the left section, an image shows the arches of an aqueduct. In the other section, an image shows a water wheel. TIM: But when people talk about hydraulics today, they’re usually referring to hydraulic machines. An image shows a bulldozer, an excavator, and a crane. TIM: These machines use pressurized liquids to do work and generate power. Like this excavator! An animation shows Tim playing with a toy excavator. MOBY: Beep? TIM: Well, no, it’s just a model, so— An animation shows Moby shooting a beam of light from his finger to the toy excavator. The toy excavator turns into a real excavator. TIM: Okay . . . An animation shows Moby, who is now wearing a hard hat, climb into the driver’s seat of the excavator. TIM: Uh, so the key to hydraulic machines are these hydraulic cylinders. An animation shows Tim point to the hydraulic cylinders on the excavator. TIM: Think of them sort of as super-powerful muscles, which can extend and contract. An image shows a group of working muscles and bones at a junction like the knee or elbow as they bend. Moby pulls one of the levers on the excavator. The arm of the excavator crashes into the ceiling. The arm then moves downward. TIM: The movement of hydraulic fluid makes all of this happen. An image shows the interior of one of the hydraulic cylinders. MOBY: Beep? TIM: No, it’s not just sloshing around in there. The fluid, usually an oil, is under very high pressure. An image shows the inner components of the excavator’s hydraulic system. TIM: When you pull those levers, a pump draws the fluid from a tank and shoots out a high-pressure stream. A motor starting is heard. An animation shows Moby pull the lever to activate the hydraulic system. Arrows travel through a tube which connects the component labeled “pump” to the component labeled “hydraulic cylinder.” A piston in the cylinder is pushed out of the cylinder. TIM: A series of tubes routes the fluid to something called the actuator, which does the real work. In this case, the actuator is a hydraulic cylinder. Moby then pushes the lever. Arrows now travel through a different tube back to the component labeled “pump.” The piston moves back into the cylinder. TIM: The pressurized fluid forces the cylinder’s piston forward and backward. An animation shows Moby pushing and pulling on the lever. The arrows and piston move according to the position of the lever. The hydraulic system begins to shake. A crash is heard. An image shows the excavator bucket sitting on top of a crushed kitchen oven. TIM: Wonderful. MOBY: Beep? TIM: Ah, good question. The secret to the incredible power of these machines has to do with the way force spreads out through a fluid. Let’s take a look at this simplified hydraulic system, which just happens to be over here for no reason at all! An image shows a hydraulic system. It is made up of two vertical pipes which connect to a horizontal pipe. The two vertical pipes contain a liquid. Inside each pipe, a piston is shown. TIM: The pistons in these cylinders are connected by an oil-filled pipe. Pascal’s law tells us that a force applied to any point within a closed amount of oil will be transferred equally throughout the oil, to every other point. An animation shows arrows pointing down at one of the vertical pipes and arrows pointing out from the other vertical pipe. As the piston in the first vertical pipe moves downward the piston in the other vertical pipe moves upward. TIM: So if I climb up on my piston, the force of my weight will push it down, and cause the other one to go up an equal amount. An animation shows Tim standing on one of the pistons. The piston is slowly moving downward while the other piston is slowly moving upward. TIM: If Moby gets on, the force of his higher weight will push his side down, and my side up, an equal amount. An animation shows Tim standing on one of the pistons and Moby standing on the other piston. The piston Moby is on moves downward while the piston Tim is on moves upward. MOBY: Beep. TIM: Ah, but watch what happens with different-sized cylinders! The surface area of Moby’s piston is 10 times bigger than this one. An image shows a hydraulic system. It is made up of a two different sized vertical pipes which connect to a horizontal pipe. Moby is seated on one of the pistons inside one of the vertical pipes and Tim is standing near the other vertical pipe. TIM: Since a force applied to this system will be transferred equally through the liquid, the amount of force I apply to my tiny piston will be carried by 10 times more fluid on Moby’s side of things. Tim is now standing on the piston. His piston moves downward while the piston Moby is on moves slowly upward. TIM: In other words, the force will be multiplied on his side! But since my piston's pushing one-tenth as much fluid, it has to move 10 units down just to make Moby's piston move one unit up. And that’s how hydraulic multiplication turns a little bit of power into a whole lot of power! An animation shows two hydraulic cylinders. An image of Tim’s head is on one of the cylinders and an image of Moby’s head is on the other. Tim’s cylinder is narrower but taller than Moby’s. The pistons inside the cylinders are moving up and down. Tim’s piston moves downward while the Moby’s piston moves upward. The distance traveled by Tim’s piston is greater than the distance traveled by Moby’s. MOBY: Beep! TIM: Yup, it probably sounds familiar because we’ve seen something like it before! Simple machines like wedges, levers, and gears trade off distance for power, too. It’s what we call a mechanical advantage. An animation shows working gears and a wedge acting as a fulcrum. MOBY: Beep? TIM: Oh no, this is just a simplified model. In a real hydraulic machine, there’s no skinny piston; instead, there are two narrow tubes pumping pressurized fluid into the much wider cylinder. An image shows the excavator. The tubes that are connected to the hydraulic cylinder are highlighted. TIM: When one tube pumps in the fluid, the piston retracts. An animation shows Moby sitting in the excavator. He pulls one of its levers, which causes the arm of the excavator to crash into the wall. A crash is heard. Moby then pushes the lever and the boom returns back to its starting position. TIM: When the other tube pumps in the pressurized fluid, the piston extends. MOBY: Beep? TIM: No, you’re right, it’s not just pistons and cylinders. It’s just that they’re really common . . . in construction sites, auto shops, braking systems, and factories the world over! An image shows an excavator dumping dirt, a car on a hydraulic lift, a disc and brake pad system from a car, and an industrial hydraulic lift. TIM: Hydraulic cylinders are basically good for two things: pushing and pulling. The other basic design for an actuator is the hydraulic motor, which creates rotation motion. An animation shows the inner workings of a hydraulic motor. A spinning driveshaft pumps fluid out that eventually feeds back into the motor. TIM: Hydraulic motors are what make this excavator’s tracks go! MOBY: Beep! A motor starting is heard. An animation shows Moby drive the excavator off screen. A loud crash is heard. The room is filled with smoke. Moby has crashed the excavator through the wall and continues to drive away. TIM: Ahh! Argh. Category:BrainPOP Transcripts Category:BrainPOP Engineering & Technology Transcripts Category:BrainPOP Science Transcripts